I have a XA-75 mongoose 21 speed and it says shimano eqiupped?
my bike is vary good and i want to know what shimano is and i want to know any tune ups i can get.
Any bike that HAS TO stamp or sticker something on the bike that says, “Shimano equipped” is hiding the fact that it’s most likely low end Shimano components. They make parts for probably 99.999% of all the bikes in the world. They range from very good to kind of poor – depending on the price of the bike.
Tune-ups on a regular basis is a good idea for any bike. You can take it to a real bike shop for a check-up at least once a year (depending on how much you ride), or learn to adjust brakes, derailleurs, etc. on your own. Many links below. A well tuned bike is a happy bike, no matter what the original cost. Even a $150 bike from Wally World will last longer if properly adjusted.
Campagnolo Centaur 10 speed drive train to Shimano 10 speed wheel